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12-01-2011, 08:56 AM   #1
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Having second thoughts about Sigma 17-50 2.8

I've ordered the Sigma 17-50mm f2.8 EX OS HSM and it should be arriving tomorrow or early next week. However, I was testing all of my lenses last night because I suspected back focusing issues after I had the cam sent in for repairs (turned out to be a false alarm, phew). The evening brought back some issues I had forgotten the severity of: I find my Sigmas to be bad performers regarding focusing.

I own Sigma 10-20mm f4-5.6, 28-70mm f2.8 Aspherical EX, 70-300mm f4-5.6 APO Macro and the most recent purchase, the 70-200mm f2.8 EX HSM

I have least experience with the 10-20mm and most with 28-70mm followed by 70-300mm (couple of thousand shots combined).

The Sigmas hunt a lot, even outdoors during sunny days but in shade - I recently used the 70-200mm at a wedding (indoors) and missed a lot of shots because it was too slow to lock. I'd say lighting was normal (whatever that means) and not low like in comfy moody place such as a bar. I've earlier used the kit lenses and the way I remember them, they focused a lot faster/hunted less.

That's why I'm having second thoughts about this 17-50mm now. I noticed earlier on with the 28-70mm that I needed something wider. The plan is to use such a lens as a general purpose lens for occasions where I don't want to switch lenses - or cant. something like indoors at parties or gatherings. I'm not too happy about carry my bag indoors, and leaving it behind at some corner is risky too.

Now I fear the lens might not help me at all, but I could be wrong - and that's why I'm writing.

I could accept the parcel and then try it - but it's one thing to try it at home and another to use it where it matters (there's a Christmas party coming up tomorrow). I don't think I should do that and then return it if I don't like it. I don't think that's fair use of the right to regret, plus there's a chance something might happen (scratches, some spilling something on it or whatever).

I'd like some insights on this one. I've tried to google and read it focuses fast - but in what lighting conditions? Haven been able to find sufficient info on that area.

12-01-2011, 09:34 AM   #2
Ole
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There is a test of that lens in Pop Photography's December issue. Perhaps they have reprinted it on their home page, might be worth a look. As I recall their only gripe was that the optical quality was below that of the 18-55 kit lens.

There are also some reviews here:
https://www.pentaxforums.com/userreviews/sigma-17-50mm-f2-8-ex-dc-os-hsm.html
12-01-2011, 09:36 AM   #3
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My wife has the Tamron 17-50 which I find amazing, if not sparking when directed towards the sun (In the review here of the Pentax, the Sigma and the Tamron the conclusion was that the best of the three in just that situation was the Tamron - shudder!). Sharpness-wise I put it on the same level as the DA50-135, that is, superb! The only primes I find in that league is FA43 & FA77 - yeah, none of my Sigmas come close!

Never had any hunting problems with the lens, as far as I can recall - the only disadvantage is the screw focusing, so not soundless!
12-01-2011, 10:00 AM   #4
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I don't really have any issues with my 2 current Sigmas. In fact, the 100-300 is a paragon of AF behavior. The 10-20/3.5 I used to have may not have been quite as reliable, I don't really remember, tbh.

12-01-2011, 10:10 AM   #5
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Thanks for the replies. I found the review on Pop Photography, but not a single word about AF performance in it

Just found this on fredmiranda:
QuoteQuote:
"Took over 4.000 field images in the past two months and had some mixed impressions. As long as there is enough light for the camera/lens to focus without flash or camera assist beam this little guy delivers great results, at ANY F stop but in particular from f. 3.5 and up. But, as soon as you bring it into dim interior (most wedding reception halls) it shows its other nature. All of a sudden, despite giving focus confirmation in the viewfinder, AF is all over the place and most often way back from the focus plane.
As soon as there is some extra light or light level in the room goes up for any reason - AF is bang-on again. Just for the reference, this seems to be exactly the same on three camera bodies. I will take it to Sigma for check-up and see if this improves, if not, this alone makes it unworkable for professional use."
Sounds pretty much like my experiences with most of my Sigma's (including decrease in AF performance with increased focals). I'm not a pro, but I often try to capture "the moment".
12-01-2011, 10:55 AM   #6
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QuoteOriginally posted by Ole Quote
There is a test of that lens in Pop Photography's December issue. Perhaps they have reprinted it on their home page, might be worth a look. As I recall their only gripe was that the optical quality was below that of the 18-55 kit lens.
The IQ on mine is on a whole different level than the kit lens. I'm looking at the review you mention and they are comparing it to the DA* 16-50, not the kit, if I'm reading that correctly.

So far I love everything about it-- it lives on my camera.

-Steve

Last edited by StevePrime; 12-01-2011 at 01:21 PM. Reason: Oops, looked up wrong lens. Fixed review link.
12-01-2011, 10:57 AM   #7
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QuoteOriginally posted by StevePrime Quote
The IQ on mine is on a whole different level than the kit lens, could you be remembering the previous model? I'm looking at the review you mention and they pretty much have only good things to say: "In all, it's a stellar performer".

So far I love everything about it-- it lives on my camera.

-Steve
The OP is talking of the Sigma 17-50mm, not of the Sigma 18-50mm.
12-01-2011, 11:01 AM   #8
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If you shoot wedding, you own yourself not to use Pentax which is not great on tracking or low EV AF. Sigma lenses will just make matter worse. Don't believe me? It's your money afterall.

12-01-2011, 11:32 AM   #9
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QuoteOriginally posted by wlachan Quote
If you shoot wedding, you own yourself not to use Pentax which is not great on tracking or low EV AF. Sigma lenses will just make matter worse. Don't believe me? It's your money afterall.
If I didn't suspect what you are saying might be true then I wouldn't have made this thread. What I'm looking for here, is for someone to convince me to go in either direction. The lens has received good reviews, but IMO low light AF performance hasn't been adressed to a degree that I was able to draw satisfactory conclusions - so I turned to this forum.
12-01-2011, 12:13 PM   #10
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My Sigma 50-150mm f/2.8 has always been a great focuser...fast and spot on. And now that my Sigma 30mm 1.4 has been calibrated to my camera, it is also a very good performer. When I owned the Sigma 170-500mm, it really impressed me with the accuracy of the focusing. And I've never had any problems with my Sigma 75-300mm in regard to AF performance.

I've read pretty much all the big reviews of the Sigma 17-50mm, as well as several other Sigma lenses I'm interested in, such as the 85mm 1.4, and I've never seen them mention a pattern of AF problems like you described. If there truly was such an issue, don't you think any of these reviewers would have noticed it at some point?

If you are having AF problems with your Sigma lenses, I would suggest that you send them to Sigma's NY headquarters, along with your camera, and let Sigma calibrate the lenses to your body. This is a great service that they offer for free as part of their warranty service. And in my case a couple weeks ago when I sent my camera and two lenses in, the turnaround time was a matter of hours, and the results were perfect.

So no, I would not send back the 17-50mm without first trying it. And with a Sigma lens, I'm not always going to be paranoid that the SDM motor will fail sometime down the road after the measly 1-year Pentax warranty.
12-01-2011, 12:31 PM   #11
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And to ad to my previous post, in regards to dim lighting, I think that the camera's AF system's speed/accuracy will be affected regardless of the lens. This has been my experience with my lenses anyway.
12-01-2011, 01:19 PM   #12
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Sorry, @Causey, I linked to the wrong review. Fixed in my post above.
12-01-2011, 01:56 PM   #13
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I've been testing and testing since I started this thread. It's been a while since I used my 55-200 DA L, so I grabbed it to refresh my memory.

I have a black plastic bag laying on the couch. A 60W bulb is placed approx 2.5m from it (under the ceiling but not shining directing down onto the bag). The bag has big white writing on it. It took about 5 attempts to get a lock with the kit lens. I tried different spots along the writing.

Same thing was virtually impossible to achieve with the Sigma 70-200 (shouldn't f2.8 vs. 5.6 make it easier for the lens to lock?)

It was easier for me to shake with the Sigma, so I had it on a tripod. If I manually focused close enough, then the Sigma would lock with perfect focus pretty much 10 out of 10 times.

Same test with the kit gave same results, except, I could get away with less precise manual focusing.

None of my lenses suffer from FF/BF issues. I'm not sure what you want me to have calibrated - besides, you suggest all my Sigma lenses needs calibrating? Sounds a bit far fetched.

I don't know whats up with reviewers - perhaps I'm currently testing under lower light than they did - there is going to be a limit at some point and although I may be wrong, it's possible they weren't close enough to it and that I'm demaning more or too much.

Also, when is fast, fast? How fast? Most we see of this kind are YouTube vids with a hand infront of the lens or with the lens cap on, so the lens can show the motors speed - or focusing on static subjects. That doesn't mean much if the lens has harder time locking under certain conditions.

And what is low light condition? Perhaps the room I did my tests in simply had too low light - perhaps not. The whole AF things is too subjective IMO.

If just one of my lenses can do the job - slow or fast, then I have that as a reference, and currently it still seems my kit lens does a better job.
12-01-2011, 02:33 PM   #14
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I tend to avoid trying to conduct synthetic, laboratory-type lens tests these days, because they are so easy for an amateur to screw up. Instead, I use my lenses in the real world for a while, and draw my conclusions from that.

In regards to the particular test you just tried, were you shooting the 70-200mm from 2.5 meters to the target? I know that with my Sigma 50-150mm, the AF is not very accurate when the subject is closer than 3 meters. I have heard that other similar lenses, such as the Pentax 50-135mm and some of the 70-200mm lenses also struggle at close distances. These lenses seem to have been designed to work optimally at longer distances, which sort of makes sense. When I'm shooting close, I have better options, such as my Sigma 30mm 1.4, or my Tamron 28-75mm 2.8.

And as far as sending all your lenses to Sigma, my thinking is that If I'm sending my camera body and one lens to Sigma for calibration, I may as well send them all since I won't be able to use them in the meantime anyway. And that way you could be sure that they are all perfectly calibrated, and any other service, such as updating the firmware, could also be performed at that time.

Last edited by Edgar_in_Indy; 12-01-2011 at 02:40 PM.
12-01-2011, 02:37 PM   #15
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For some reason, your location is not listed under your name, but I just looked at your profile and saw you're in Denmark. My advise about sending your camera and lenses to Sigma to be checked and calibrated was made under the assumption that you're in the US. My experience with Sigma service in the US is very good, but in your part of the world I don't know if it would be the same quick and positive experience.

Last edited by Edgar_in_Indy; 12-01-2011 at 03:05 PM.
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